Regime: Purchase with Armory Key in the Archives (D2).
Flashpoint: Available with Season Pass.
Red Son: Gamestop pre-order exclusive.
New 52: Special Edition exclusive.

Original Doomsday costume display
Enter the Fortress of Solitude Arena with two characters playing Doomsday, with one person wearing the Insurgency costume and the other person the default costume. The Doomsday on display at the back of the level will be wearing the costume from Death of Superman.